#include "asio.hpp"
#include <iostream>
#include <memory>
#include <utility>
#include <vector>
#include <ctime>

using asio::ip::tcp;

// A reference-counted non-modifiable buffer class.
class shared_const_buffer
{
public:
    // Construct from a std::string.
    explicit shared_const_buffer(const std::string& data)
        : data_(new std::vector<char>(data.begin(), data.end())),
          buffer_(asio::buffer(*data_))
    {
    }

    // Implement the ConstBufferSequence requirements.
    typedef asio::const_buffer value_type;
    typedef const asio::const_buffer* const_iterator;
    const asio::const_buffer* begin() const { return &buffer_; }
    const asio::const_buffer* end() const { return &buffer_ + 1; }

private:
    std::shared_ptr<std::vector<char>> data_;
    asio::const_buffer buffer_;
};

class session
    : public std::enable_shared_from_this<session>
{
public:
    session(tcp::socket socket)
        : socket_(std::move(socket))
    {
    }

    void start()
    {
        do_write();
    }

private:
    void do_write()
    {
        std::time_t now = std::time(0);
        shared_const_buffer buffer(std::ctime(&now));

        auto self(shared_from_this());
        asio::async_write(socket_, buffer,
                          [this, self](std::error_code /*ec*/, std::size_t /*length*/)
        {
        });
    }

    // The socket used to communicate with the client.
    tcp::socket socket_;
};

class server
{
public:
    server(asio::io_context& io_context, short port)
        : acceptor_(io_context, tcp::endpoint(tcp::v4(), port))
    {
        do_accept();
    }

private:
    void do_accept()
    {
        acceptor_.async_accept(
            [this](std::error_code ec, tcp::socket socket)
        {
            if(!ec)
            {
                std::make_shared<session>(std::move(socket))->start();
            }

            do_accept();
        });
    }

    tcp::acceptor acceptor_;
};

int main(int argc, char* argv[])
{
    try
    {
        if(argc != 2)
        {
            std::cerr << "Usage: reference_counted <port>\n";
            return 1;
        }
        asio::io_context io_context;
        server s(io_context, std::atoi(argv[1]));
        io_context.run();
    }
    catch(std::exception& e)
    {
        std::cerr << "Exception: " << e.what() << "\n";
    }
    return 0;
}